The Proof Widget

Logical System


Some predicate logic proofs or derivations using Gentzen calculus. Try to prove them. Click on a line to select it. Select one or more lines, apply the appropriate rule off the Rules menu. (Click 'Derive It' off the Wizard Menu, if you want help).

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Tutorial 25 ...

Logical System

You now have the tools to appraise arguments to the level of detail offered by predicate logic.

Let us run through how these might be used with a long and difficult example.

Consider the argument

Tutorial 23: The semantics of relations

Logical System

The Tutorial

The semantics of relations proceeds in much the way one would expect-- the new item that has to be taken account of is the order of the terms (because, for example, Tab is not at all the same thing as Tba -- Arthur being taller than Beryl is not the same as Beryl being taller than Arthur).

Let us start with an Interpretation

Interpretation 1

Universe= {a,b}